1. Field of the Invention
The present invention relates to a fingerprint reading method of acquiring a fingerprint image of a finger and generating feature information of the fingerprint on the basis of the image. In particular, the present invention relates to a fingerprint reading method using the so-called sweep type fingerprint sensor to successively acquire a series of partial fingerprint images representing a fingerprint from a finger which conducts slide operation.
2. Description of the Related Art
Heretofore, personal authentication using a fingerprint is widely spread not only to identify a suspect in the police and judicial fields, but also as means in the general society for determining whether a person can be admitted to enter a room or whether a person can use an apparatus. Recently, it is also attempted to mount a mechanism which conducts such personal authentication by using a fingerprint, on a portable information device. In that case, it is demanded to make the size of the authentication mechanism small to the utmost.
As means satisfying the demand described above, a sweep type fingerprint sensor which successively reads fingerprint images from a finger which slides on a sensing surface having a lateral width equivalent to the width of the finger is known. Images obtained from the sweep type fingerprint sensor are no more than partial images corresponding to parts of the fingerprint. In order to obtain information which indicates where in a general image the acquired partial image is located, therefore, a method of joining partial images read by the sensor and reconstructing the general fingerprint image is adopted.
Techniques concerning this method have been disclosed in Japanese Patent Application Laid-Open Nos. 10-091769 and 2003-331269. According to the techniques, the general fingerprint image is reconstructed by successively superposing read partial fingerprint images one on another and the general fingerprint image is used to register and collate personal information.
According to the techniques disclosed in Japanese Patent Application Laid-Open Nos. 10-091769 and 2003-331269, it is possible to prevent a missing place from occurring in the general fingerprint image by superposing acquired partial fingerprint images one on another. According to the techniques, however, all partial fingerprint images read by the sensor are stored in a buffer memory and then the general fingerprint image is reconstructed. Therefore, a vast memory space is needed to conduct buffering. In addition, there is an inconvenience that the next processing of generating feature information of the fingerprint cannot be resumed until all partial fingerprint images are collected and the general fingerprint image is completed.